There are a number of hoops to jump through in order to serve
XHTML with MathML that is usable by all of IE 6, Moz 1, and NS 7.
There were a few points that I missed in the doc, and without looking
back I'm not sure just what, so let me review for possible comment
what I think are the subtleties. They seem to be right in the sense
that they "work" in present time.
1. The document must be served through HTTP as "text/xml".
2. The document must not reference external XML entities.
3. The document must not have a "<!DOCTYPE" declaration.
4. All style sheet references, CSS or XSL, must be to relative URI's
(or at least, I think, URI's on the "same server", but the meaning
of that is slightly amibiguous).
5. The reference to one's local copy of David Carlisle's XSLT sheet
"mathml.xsl" (or "pmathml.xsl") must be via '<?xml-stylesheet
type="text/xsl"' before the root element (which, of course, must
be opened with '<html xmlns="http://www.w3.org/1999/xhtml"').
6. XSLT sheets must be served through HTTP as "application/xml".
(See RFC 3023; "text/xsl" is not a registered content type.)
7. CSS sheets must be served through HTTP as "text/css". (See
RFC 2318.)
-- Bill